drm/i915: set more FBC chicken bits

Add a couple of missing workaround bits for ILK & SNB.  These disable
clock gating on a couple of units that would otherwise prevent FBC from
working.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 98967f3..d2ef1c2 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -6286,7 +6286,9 @@
 
 		if (IS_GEN5(dev)) {
 			/* Required for FBC */
-			dspclk_gate |= DPFDUNIT_CLOCK_GATE_DISABLE;
+			dspclk_gate |= DPFCUNIT_CLOCK_GATE_DISABLE |
+				DPFCRUNIT_CLOCK_GATE_DISABLE |
+				DPFDUNIT_CLOCK_GATE_DISABLE;
 			/* Required for CxSR */
 			dspclk_gate |= DPARBUNIT_CLOCK_GATE_DISABLE;